Figured I'd make a post about this to make everyone aware of this:
So in the Suramar quest line you unlock the Court of Stars dungeon at 6000/12000 honored rep with The Nightfallen, which takes the entire quest line up to that point and a few days of Nightfallen world quests
The Warrior campaign has a quest "Greater Power" which requires getting a drop off the 2nd boss of Court of Stars and killing the last boss
In order to unlock the third relic slot we have to finish the warrior campaign which this is a pivotal part of
Previously in the beta Court of Stars was available on N/H/M but as of today is Mythic only, in addition to that no other class has their third relic slot (30-40 ilvls) gated behind a rep grind, and now it's gated behind a mythic dungeon AND a rep grind.
In my experience on the beta it doesn't seem like the fact it's mythic will be a big deal, but for a lot of players it might be especially when combined with the rep grind.
It doesn't seem apparent if Blizzard is going to change it but as of the current build today it still requires the item from Court of Stars